The present invention relates to a reflective screen for use in a front-projection television, in which picture images reproduced on CRTs or a liquid crystal projector, which is placed on the front side of said screen, are projected onto the screen.
Conventional reflective screens for the front-projection television include a mat screen, a screen having an aluminum film reflection surface, and a Fresnel lens screen.
In the mat screen, the diffusion characteristic of reflection light in the vertical and horizontal directions is improved by such measures as making uneven the surface of a cotton cloth or plastic sheet, or sticking small beads to the surface of such a material.
In the aluminum screen, the diffusion characteristic of reflection light is enhanced by forming a highly reflective aluminum film on a back-reinforced plastics (base material) by, e.g., vapor deposition or sticking, and further processing the aluminum film to have minute convexes.
In the Fresnel lens screen, the front surface or back surface of a lens plate is formed into a Fresnel lens surface, and a reflection film is provided on the back side of the lens plate. This type of screen has a large screen gain without occurrence of hot spots, and a wide viewable range.
However, it is inevitable in the above screens for the front-projection television that the screen reflects not only incident light from the CRTs (LC projector) but also ambient light, in accordance with its reflectivity. This causes the screen to become brighter in proportion to the intensity of ambient light, i.e., the brightness of a room. Therefore, it may result that a dark portion of a picture image cannot be seen well because its brightness on the screen become comparable with that of ambient light. In other words, it is difficult in a bright room to obtain sufficient performance of contrast.